They said it had helped to cut junk food sales in other countries including France, Finland and Mexico.

And the cash raised from taxing food high in fat, sugar and salt could be used to fight obesity, said the Food Research Collaboration.

Nearly two thirds of adults in England are either overweight or obese.

The associated health problems cost the NHS more than £5billion every year.

FRC chief Prof Tim Lang added: “Food taxes must be explored, not least because everybody pays in the end through NHS costs or lost quality of life.

Obesity: Tax junk food (Image: Getty)

“Governments have for too long been in a fantasy world where cheap food is celebrated as a good thing, without including the externalised costs in the form of ill-health, rising healthcare costs and lost human potential.

“Food taxes may make politicians nervous but must be explored, not least because everybody pays in the end through NHS costs or lost quality of life.”

Obesity costs the NHS more than £5billion a year.

Nearly two-thirds of adults in England are overweight.

And , the price of unhealthy foods has been shown to be decreasing over time while the gap between the price of healthy and unhealthy foods is widening, experts have said.